In recent years there has been a rapid development of so-called “smart” tyres, i.e. tyres provided with electronic systems that enable certain parameters to be measured, such as the inflation pressure, the temperature of the tyre, or external forces exerted on the tyre during rolling. Such tyres are generally also provided with electronic systems that enable the measurements so obtained to be transmitted to the vehicle on which the tyre is mounted. For the sake of brevity, in what follows the measurement and/or transmission systems will be referred to indiscriminately as “electronic systems”.
Such electronic systems are very often located inside the tyre. They can be fixed directly onto the tyre itself, for example in a pocket formed on an inside wall of the tyre; patent application U.S. Patent Application Publication No. 2005/0217774 describes an example of this. Another way to fix an electronic system inside a tyre is to use a “patch” which is glued onto an inside wall of the tyre (see for example the U.S. Pat. No. 6,782,741). A third possible approach is to attach the electronic system integrally to the tyre's inflation valve: U.S. Pat. No. 6,278,361 describes a design in which sensors are arranged in a case which is attached to the valve. The present invention relates to this third approach.
Nowadays many types of valves are available, which are designed for very different uses. In the field of passenger cars, in particular, valves are known which are fixed onto the wheel rim by screwing (“clamp-in” valves): the valve body is inserted into the valve hole from radially outside the rim (corresponding to the inside of the tyre volume after the tyre has been mounted) and is locked in place by a nut screwed on from radially inside the rim. The valve front has an annular recess to accommodate an annular sealing joint.
Another type of valve, which is fixed by clipping into place, is known as a “snap-in” valve. In such valves the (usually metallic) tube that encloses the actual valve mechanism is anchored in a valve body, for example made of rubber. The valve body has a peripheral groove to receive the edge of the valve hole. The invention concerns valves of this type, an example of which is shown in FIG. 1. An example of a “snap-in” valve comprising an electronic system is described in the U.S. Pat. No. 6,005,480. Other examples can be found in documents U.S. Pat. No. 6,851,308 and WO 2005/123421.
A “snap-in” valve is fitted (see also FIG. 7) before the tyre is mounted, by positioning the valve on the radially outer side of the rim (corresponding to the inside of the tyre volume after the tyre has been mounted), then inserting the head of the valve through the valve hole, and then using a tool to pull this valve head until the edge of the valve hole is engaged within the peripheral groove of the valve body. A liquid (for example soap solution) is generally applied during this operation to facilitate the fitting of the groove over the valve hole. Gas-tightness is ensured by leak proof contact between the edge of the valve hole and the valve body.
In general the valve is destroyed by removing it. For example, the same type of tool that was used to fit the valve is used to pull the valve head until the entire valve body comes out through the valve hole.
When an electronic system is attached to the valve, the valve is fitted in a strictly analogous manner taking care, however, not to damage the electronic system. Removal may be more complicated, especially when the electronic system is of some size. It is then necessary to separate the valve and the electronic system before the valve is removed. This may entail first taking off the tyre, with some risk of damaging the electronic system.